In some medical applications, for example in the field of dental anaesthesia, it is necessary to pass through dense tissue, e.g., the cortical bone of a jawbone so that it is possible to inject a pharmaceutical product at the proper site. To arrive thereat, first a drill is used for perforation followed by injection using a needle. In this case, the perforation hole must be located with the injection needle. Additionally, since the injection needle is of smaller diameter, there is risk of leakage of the pharmaceutical product via the perforation hole during injection. Also, this two-step application requires the use of two different instruments, namely a perforator and a syringe, which increases operating time.
According to an alternative method, a perforator needle is used for perforation and for injection. This saves time and avoids leakage of pharmaceutical products, since the perforation hole is of the same diameter as the needle. However, this alternative method gives rise to the problem of obstruction of the needle lumen on account of debris generated during perforation. One solution consists of injecting a liquid between each entry phase of the needle to clear the lumen of any debris, but the efficacy thereof is limited.
By choosing a suitable rotation speed for the perforator needle or by using a needle with specific bevels, it is possible to arrive at reducing, but not eliminating, the level of needle obstruction.